High-frequency spark circuit



March 11, 1947. H. BENloFF 2,417,052

HIGH-FREQUENCY SPARK CIRCUIT i Filed Feb. 25, 1942 5 Sheets-Sheet l HUGO BENIOFF March ll, 1947. H, BENIOFF 2,417,052

HIGH-FREQUENCY SPARK CIRCUIT Filed Feb. 25, 1942 3` sheets-sheet 2 INVENTOR HUGO BENIOFF BY ATTORNEY H, 1947. H. BENloFF l HIGH-FREQUENCY SPARK CIRCUIT 3 Sheets-Sheet 3 Filed Feb. 25. 1942 INVENTOR HUGO BENIOFF 'Nwllllliii i t ,|11

Patented Mar. 11, 1947 MGH-FREQUENCY SPARK CIRCUIT Hugo Benioff, La Canada, Calif., assigner, by

mesne assignments, to Submarine Signal Company, Boston, Mass., a corporation of Delaware application February 25, 1942, serial N'o. 432,293

(o1. csa-38) Claims. 1

The present invention relates to apparatus for producing high frequency electromagnetic Waves and relates more particularly to short wave apparatus in the one-meter range and lower, or 390 megacycles and higher. f

The present invention` further applies to damped wave trains as contrasted to the production of continuous oscillations and is an improvement along the lines of the apparatus disclosed in my copending applications Serial Nos. 362,434, led October 23, 1940, and 391,353, led April 30, 1941.

In the earlier developments in radio transmission, spark circuits were used quite extensively. ln such spark circuits resonance was chiefly controlled by a coil and a condenser in series with the spark and for the most part other distributed capacities and inductances could be neglected. In a spark oscillator the available output energy is derived from the electrostatic energy stored in the capacity 0i the system at the moment the spark breaks down the gap. In an oscillator designed for extremely high frequencies the capacity for resonance is necessarily eX- tremely small and consequently the oscillator should be constructed in such a form to provide a maximum capacity for the required frequency which is one of the chief objects or the present invention.

The applicant has also discovered that due to the fact that currents of extremely high radio frequencies ilow on the surface of the conducting elements, resistances of large magnitudes may accidentally be incorporated in the high frequency circuits on account of ssures, cracks or poor joints in the surface of the electrical conducting elements. These dawg may not be particularly visible to the eye and yet they may be sufficient to cause the current to flow by longer paths and thereby introduce resistance and reactance in the oscillatory circuit which may change the frequency or even prevent oscillations entirely. It is particularly important in places Where the current density in the system is high, as, for instance, around the sparking points which should be of tungsten or other high melting-point metals, that the surface be particularly smooth and free from fiaws or cracks, as cracks in these portions oi the surfaces are particularly eiective in increasing the electrical losses in the oscillatory circuit.

The present invention is particularly adaptable for transmitting signals in a radio distance measurement system operating by means of the time .ci travel of a radio wave to and from a radio reflecting object. For this purpose there is incorporated in the present invention a special trigger circuit including a gaseous. Control tube having a grid control element which brings about a rapid discharge of a condenser through one circuit ,Causing a cha-reins 0i the capacity in the radio frequency oscillating Circuit. The control grid in the trigger circuit uis `energized by repeated peaked periodic impulses which initiate the ,discharge o f the condenser in the circuit coupled to the radio frequency oscillating circuit.

The system according to the present invention 4may .be @related with suitable kind of indieating mechanism for measuring the time interyal between the transmission of the direct wave train and the receipt of the reflection. Such indicating mechanism, for instance, may include a cathode ray-tube in which the motion of the spot on the fat? Gf the tube may be controlled to provid@ the time interval measurement- .Other advantages oi the present invention will `be more fully understood in connection with the speciiications set forth in the description below taken in ,connection with the drawings showing an embodirvnent of the invention in which Fig. 1

.shows the invention `partially Ain fragmentary secsitioned a sealed housing comprising a chamber 2 ,containing the antenna elements 3 and the 0sciilator ,6 and an additional chamber 5 containing :high voltage supply apparatus. These two chambers are open one to the other `through the perforation 6 in the supporting partition l and may be filled with a gas such as nitrogen or oxygen through the valve 8, or `they may be evacuated to 'low vacuum, if desired. The chamber 2 is sealed ofi from the throat of the horn by a member transparent to radio Waves as, for instance, a rubber or Bakelite plate 9. The chamber 5, it will be noted, may be formed of two parts, a collar section Il With a flange lil and a cap Section l2 with a flange `I3 so that the chamber may be opened for the-purpose of making changes or substituting or renewing parts therein. The iianges may be made airtight Vby sealing vthem with a gasket I4 in between, and, similarly, the ange l5 of the collar may be sealed to the cuter wall of Ythe chamber 2 With an airtight gasket lo in between the `flange and the wall. Mounted .on

4I. posite and parallel relationship to the inner sur- 3 the partition 1 is an insulating block I1 providing the support in connections for the impulse transformer i8. This transformer comprises alow-voltage primary I9 wound on a Bakelite tube 25 about which is a layer of wax 2l separating and spacing the Bakelite tube 20 from the glass tube 22 on the exterior of which is wound the high-voltage coil 23. Connections to the lowvoltage coil i9 are brought out to the terminals 24 and 25 on the supporting block l1 from which connections are made to the supply terminals and switch 2G at the side wall of the chamber 5. The terminals 29 and 29 0f the high frequency coil 23 are mounted on the insulating rings 21 and 28 at the ends of the glass shell. is conducted to the terminal 29 over the line 3U from the choke coil 3l whchwill presently be described. The secondary circuit is completed at its other end over the connector 32 to the spark oscillator 4 over the conductor 33 and through the auxiliary spark gap 34 to the other end of the choke coil 3l.

The oscillator in the present case may comprise a plate 35 of conductive material having integral therewith at its periphery a flange member 36 extending outward from the surface of the plate, The ange member 38 has a fiat end surface 31 upon which is mounted a flat annular member 38 preferably of mica or some material having good insulating qualities. This annular mica flat member is held fast to the surface 31 of the flange 35 by means of suitable screws 39 or by any other suitable means and supports nearer its inner periphery a component part 45 of the tank circuit. This part 45 comprises a flat conductive disc element il which is held near its periphery by the screws 42 to the mica member 38. The flat disc 4l has projecting from the center thereof and integral therewith the antenna or rod element 43 which may be perforated and slotted in slots 44 at the end to receive an adjustable member 45 for tuning the antenna. Opposite this antenna member 43, where it projects from the disc 4I and on the inner surface of the disc, is a sparking point 46 which is preferably made of tungsten or other material having a Very high melting point. This tungsten point 4S is carefully mounted in the -face f the disc 4I first by welding nickel to tungsten, then silver soldering nickel to the plate, as indicated in Fig. 1.

After this, the whole disc and point are turned down until all cracks and fissures have been removed so as to permit a free flow of current from the point to the adjacent surface of the disc The surface of the disc 4l is placed in opface :i3 of the plate 35. At the center of the surface 43 of the plate 35 there is mounted a tungsten point 49. The same care is taken with the construction and mounting of this `point as with the point 46. The plate 35 is spaced slightly away at its periphery from the partition 1 by the rearwardly extending peripheral ring 55 through which the oscillator is clamped to the partition by mea-ns of the groups of screws passing through the partition into the end ring 36. The plate 35 is also provided with a central boss element 52 against which a set screw 53 passing through the partition 1 presses. This set screw may be used to adjust the distances between the two sparking points 4G and 49 to the desired distance which usually is approximately ten thousandths of an inch. After the desired setting has been obtained, the locking nut 54 may be used to lock the screw in position. The apparatus is Power 4 also provided with an auxiliary spark gap 34, as mentioned above, which has two point electrodes 55 and 55. These electrodes may be encased in an insulating tube 51 which is provided with an opening or window y53 through which the points may be observed to see that they are properly spaced. The points may be held in the tubes in a drive nt so that the distance of the sparking points may be properly adjusted.

The elecetrode 55 is connected to the choke coil 3l which may be of a special construction comprising a tapered core member 553 wound with coarser turns 6i] at its small high voltage end gradually becoming nner as the tapered diameter increases. The purpose of this choke is to prevent the high frequency current from flowing back intovthe supply circuit. The spacing between turns is greatest at its small end nearest the oscillator since the danger of spark-over is the greatest there. By this construction the impedance coil will have less loss than otherwise in the high frequency circuit and will also stand up more efficiently against the higher voltage. The oscillatory circuit in the present instance comprises the surface 43 of the plate 35 and the surface 5l of the disk 4l with the sparking points 45 and 49 and the gap as the central part of the system. Coupled to this oscillatory circuit is a second oscillatory circuit tuned to it, by means of which the radio waves are radiated into the propagating medium. This circuit comprises the antenna element made up of the pole member 43 with its adjustable extensible rod 45 and the outer surface of the plate 4|. The pole member 43 with its extension 45 is approximately M4 or one-quarter of the wave length corresponding to the frequency of the oscillatory circuit. The surface of the plate from the pole out to the edges furnishes the counter-poise for the pole, making an oscillatory node somewhere near the base of the pole member 43. This last circuit is coupled to the oscillatory circuit previously described and through this coupling the energy is delivered from the oscillatory circuit including the spark gap to the antenna oscillatory circuit including the pole from which the electromagnetic waves are radiated. The energy stored up in the oscillatory circuit between the surfaces 6I and 48 is in the form of an electrostatic eld produced between these opposing surfaces and this circuit is coupled to the antenna circuit through the potentials and current set up on the opposite surfaces of the plate 4I by reason of the conductive coupling between the inner and outer surfaces of plate 4| at the edge of the plate. When the charge existing between the plates 35 and 4| is such as to cause a break-down of the resistance across the sparking points, the charges on the plate produce or result in surface currents which flow back and forth across the spark gap with the frequency established by the capacity and inductance of the circuit which depends upon the dimensions and shape of the resonating structure and dielectric constant of the medium between the plates.

In the operation of the circuit there is evidence that in addition to its other functions the auxiliary gaps have the effect of increasing the rate at which the oscillatory circuit charges which aids in building up the potential across the plates of the oscillatory circuit to a maximum value at the point when the discharge occurs.

The resonance established by the osillator embracing tl'ze surfaces 6| and 48 of the plate and the 'sparking points is that of one-half wave ammore length, the extending rod element 43 and its Vextension c5 forming an approximately one- `quarter wave length member and the outside sur- Aface of the disc A1| furnishing the counter-poise.

In the arrangement shown in Fig. 2 the oscillatory circuit is symmetrical on both sides of the sparking electrodes lf3 and Il. Each of these electrodes 7B and '5| is mounted at the center of opposing plates l2 and 13, respectively. From the outer surface at the center of these plates extend the radiating antennae 'M and 15, respectively, which .are tunable by the adjustable rods 'i6 and ll, respectively, which may be moved `outward or inward in recesses formed at the ends of the rods. The plates 12 and 'i3 are held in position, each by annular mica iiat members 18 `and 'i9 to which the plates I2 and 'i3 are clamped -by means of the screws Si), 35i, etc., and 8|, 8|, etc., respectively. These mica annular fiat members are supported by a ring 82 to which the members 18 and .19 are clamped near their outer periphery by the screws 83, 83, etc., and 84, 8%, etc., respectively. The ring 82 is supported by lan insulating member 85 to which it may be clamped or cemented and which, in turn, is

clamped or cemented to the reflecting parabola `8.6 at its center. High-tension voltage is conducted to the oscillatory circuit formed by the plates l2, i3 and the electrodes lil and 7| over :the `wires El and BB which are connected to the auxiliary spark electrodes 39 and SEB, respectively, which, in turn, respectively are connected in the cham-ber 93 to the chokes 9| and 92. The high- `tension winding 96 of the impulse transformer :has its terminal leads @d and 35 connected respectively to the chokes Si and 92. The impulse transformer 91 is similar to the one described in connection with Fig. 1 and is provided with a primary winding 98 to which power is supplied by the lines Q9 from the switch |06 'which eonnects to leads `externally of the hermetically sealed casing im.

The chamber @3 may also contain gases under pressure but if it is desired to permit the cham- -ber to be `exposed to the atmosphere, provision is made for inserting a moisture-absorbing substance within the casing. For this purpose a threaded cylindrical holder ifi? may be mounted .at the side ci the casing and may contain a cartridge |93 containing some moisture-absorbing substance 1i ifa-l, for instance, calcium chloride or .the like. This substance in the cartridge is eX- posed through perforations |65 therein to the air or other gas medium in the chamber without, of course, permitting the substance to drop or fall out of the cartridge into the chamber. The oscillatory circuit may also be sealed by placing a hood it of insulating material over the front of the parabola at the center where the oscillatory circuit is placed. If the apparatus is used without special gas pressure, it is still desirable, in order to exclude the moisture, to enclose the oscillatory circuit and the other high-voltage ap- .paratus In the arrangement indicated in Fig. 2 the radiating members '55 and 'Vi and the outside of the 'plate 73 and the radiating members 'I6 and ld and the outside of the plate 'l2 form resonant circuits tuned with and coupled to the oscilla- `tory circuits formed by the internal surfaces of the plates '52, '53. The resonance of the oscillating circuit formed by the inner surfaces of the `plates 'i2 and 13 and the sparking electrodes establish the oscillatory frequency of the high frequency radio circuit. The energy stored up by Cil virtue 'of the rcharge across the plates 12 and `I3 'is the Vmaximum amount of energy obtainable in the oscillatory circuit which commences to oscillate .at the linstant Athat the discharge occurs across the sparking electrodes. The external circuit just previously .mentioned is coupled to this circuit and `acts to radiate the high-frequency electromagnetic waves.

In .the arrangement indicated in Fig. 2, two lauxiliary,sparking electrodes 89 and 90 are employed as well as two choke coils 9| and 92 which are of the same type previously vdescribed in connection with Fig. 1.

In the arrangement indicated in Fig. 4 there is shown an operating circuit for operating the apparatus `shown either in Figs. 1 or 2. This circuit comprises in the main two parts, one a sweep circuit which .is of the normal type produciing a square-top wave from 'the output ofthe tube |3|. `This square-top wave is somewhat modified vby `.the condensers |32 and |33 to produce fa peak on'the forward Cornel` of the squaretop wave so that in the output lines |34 the wave may simply be represented as a sharp peak. The tiring circuit is shown within the dotted-line diagram |35 and comprises a gaseous control tube |35 whose input circuit is biassed by rectied current supplied through a low-voltage rectiiier |31. A high-voltage rectifier |38 is used to energize the condenser |39 `which is carged through the primary Ui of the impulse transformer |4| corresponding to that indicated in Figs. 1 and 2. When the peak of the control wave from the cir- ;cuit |355 is impressed upon the grid |42 of the thyratron |36, the tube |35 fires with the result that `the charge on the condenser |39 is discharged through the primary of the impulse transformer, thus setting up a high-voltage discharge across the secondary of the transformer which rapidly builds up to a break-down the poten-tial across the sparking electrodes of the oscillatory circuit. lThe thyratron tube |36 may be operated `periodically at the rate 0f oscillations in the sweep circuit |36. This period may be 5000.01- 10,00() vibrations a second, if desired. The length of the discharge across the high-frequency oscillatory circuit may be of the order of vone micro-second and the frequency established by the oscillatory circuit may have a wave length of ten centimeters -or more or less, if desired, vcorresponding to 3000 megacycles or somewhat more or less, whatever may be desired.

Having now described my invention, I claim:

l. A short wave oscillatory spark circuit comprising means providing two at surfaces, means centrally located on said surfaces and projecting therefrom forming a spark gap, means insulatingiy supporting said .first means with said two fiat surfaces in closely spaced opposed relationship to each other, said surfaces, the space between them and said spark gap means being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current iiow across the gap an oscillatory circuit resonant at the frequency of said oscillations, and

an energy-radiating circuit tuned to the same frequency as said oscillatory circuit conductively coupled to the latter.

2. A short wave oscillatory spark circuit comprising means providing two fiat surfaces, means between them and said spark gap `means being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current flow across the gap an oscillatory circuit resonant at the frequency of said oscillations, and conducting means extending outwardly from said rst means at least from one of said opposed surfaces and forming with the opposed surface from which it extends a radiating means resonantly coupled with said resonant oscillatory circuit.

3. A short wave oscillatory spark circuit comprising two flat plates, means forming a spark gap located at the centers of the surfaces of said plates, means insulatingly supporting said first means with the flat surfaces of said plates in closely spaced opposed relationship to each other, said surfaces, the space between them and said spark gap means being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current flow across the gap an oscillatory circuit resonant at the frequency of said oscillations, and an energy-radiating circuit tuned to the same frequency as said oscillatory circuit conductively coupled to the latter, said radiating circuit including a conducting member extending outwardly from at least one of said plates substantially opposite the location of said spark gap and the outer surface of the plate from which it extends.

4. A short wave oscillatory spark circuit comprising two flat plates, means insulatingly supporting said plates with the inner surfaces thereof in closely spaced opposed relationship to each other, a pair of sparking electrodes one mounted on and projecting from the inner surfaces of each of said plates substantially at the center thereof, said surfaces, the space between them and said spark gap means being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current flow across the gap an oscillatory circuit resonant at the frequency of said oscillations, and an energy-radiating circuit tuned to the same frequency as said oscillatory circuit conductively coupled to the latter, said radiating circuit including a radiating pole member projecting from the outer surface of one of said plates substantially opposite the point of the sparking electrodes.

5. A short wave oscillatory spark circuit comprising two flat plates, means insulatingly supporting said plates with the inner surfaces thereof in closely spaced opposed relationship to each other, a pair of sparking electrodes one mounted on and projecting from the inner surfaces of each of said plates substantially at the center thereof and a pole member projecting from the outer surface of one of said plates substantially opposite the point of the sparking electrodes, said pole member with the external surface of said plate forming a radio frequency radiating resonator and the inner surfaces of said plates together with the sparking electrodes forming an oscillatory resonator, both of said circuits being adjusted for substantially the same resonant frequency. l

6. A short wave oscillatory spark circuit comprising means providing two flat surfaces, means forming a spark gap located substantially between the centers of said surfaces, means insulatingly supporting said first means with said two fiat surfaces in closely spaced opposed relationship with each other and conducting means extending outwardly from said first means at least from one of said opposed surfaces, said conducting means and the surface from which it extends forming a tuned radiating radio frequency oscillatory circuit and said opposed surfaces with said spark gap forming a tuned oscillatory circuit, said circuits being coupled together and tuned substantially to the same resonating frequency.

7. A short wave oscillatory spark circuit coniprising two fiat plates, means insulatingly supporting said plates with the inner surfaces thereof in closely spaced opposed relationship to each other, a pair of sparking electrodes one mounted on and projecting from the inner surfaces of each of said plates substantially at the center thereof, said surfaces, the space between them and said spark gap means being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current flow across the gap an oscillatory circuit resonant at the frequency of said oscillations, and an energy-radiating circuit tuned to the same frequency as said `oscillatory circuit conductively coupled to the latter, said radiating circuit including pole members projecting from the outer surfaces of said plates substantially opposite .the position of said sparking electrodes.

8. A short wave oscillatory transmitter comprising two flat plates having pole members extending outwardly from the surface of said plates, means insulatingly mounting said plates with the other surfaces in closely spaced parallel opposed relationship to each other and means forming sparking electrodes at the center of said plates between said opposed surfaces, said surfaces, the space between them and said sparking electrodes being dimensioned with respect vto the wave length of the oscillations to be generated so as to form upon current flow across the electrodes an oscillatory circuit resonant at the frequency of said oscillations and said pole members and the outer surfaces of said plates being dimensioned to form a second oscillatory circuit resonant at substantially the same frequency as said first oscillatory circuit, and means for energizing said rst oscillatory circuit.

9. A short wave oscillatory circuit comprising two fiat plates having pole members extending outwardly from the surface of said plates, means insulatingly mounting said plates with the other surfaces in closely spaced parallel opposed relationship to each other and means forming sparking electrodes at the center of said plates between said opposed surfaces comprising a pair of projecting electrodes of a substantially high meltingpoint metal mounted on and projecting from the center of the opposed surfaces of said plates, said surfaces, .the space between them and said sparking electrodes being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current flow across the electrodes an oscillatory circuit resonant at the frequency of said oscillations and said pole members and the outer surfaces of said plates being dimensioned to form a second oscillatory circuit resonant at substantially the same frequency as said first oscillatory circuit, and means for energizing said first oscillatory circuit.

l0. A short wave oscillatory circuit comprising two flat plates having pole members extending outwardly from the surface of said plates, means insulatingiy mounting said plates with the other surfaces in closely spaced parallel opposed relationship to each other and means forming sparking electrodes at the center of said plates between said opposed surfaces comprising a pair of projecting electrodes of a substantially high meltingpoint metal mounted on and projecting from the center of the opposed surfaces of said plates, said sparking electrodes and said plates joining each other in a substantiahy smooth surface, said surfaces, the space between them and said sparking electrodes being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current iiow across the electrodes an oscillatory circuit resonant at the frequency of said oscillations and said pole members and the outer surfaces of said plates being dimensioned to form a second oscillatory circuit resonant at substantially the same frequency as said first oscillatory circuit, and means for energizing said first oscillatory circuit.

l1. A short wave oscillatory circuit comprising a pair of electrically conductive disk members each having pole elements extending from the surface of said disks on one side at the center thereof, a pair of sparking electrodes mounted on the other side of said disks at the center thereof, a pair of fiat annular insulating elements clamped to said disks, a ring member supporting said fiat annular members, said elements together positioning said disks with the surfaces on which said electrodes are mounted in closely spaced parallel relationship with each other with the sparking electrodes in opposed positions and electrical conducting means connected to said disk members at their peripheries for supplying power to said oscillatory circuit.

12. A short wave oscillator circuit comprising a pair of electrically conductive disk members each having pole elements extending from the surface of said disks on one side at the center thereof, a pair of sparking electrodes mounted on the other side of said disks at the center thereof, a pair of flat annular insulating elements clamped to said disks, a ring member supporting said flat annular members, said elements together positioning said disks with the surfaces on which said electrodes are mounted in closely spaced parallel relationship with each other with the sparking electrodes in opposed positions and electrical conducting means connected to said disk members at their peripheries for supplying power to said oscillatory circuit, the said pole members having adjustable extension means for varying the effective length thereof whereby the radiating circuit formed by the pole members and the external surfaces of the disks may be adjusted to the natural frequency of the oscillatory circuit.

13. A short wave oscillatory spark circuit comprising a pair of plate members, means mounting said plate members insulatingly supporting one from the other with the surfaces thereof in parallel opposed spaced relation to each other, a pair of sparking electrodes supported at the center of said surfaces in opposed relation to each other and a pole member extending from one of said plates from one of the unopposed surfaces and means mounted opposite the back of the other of said plates for adjusting the position of one of said electrodes with relation to the other thereof, said surfaces, the space between them and the sparking electrodes being dimensioned with respect to the wave length of the oscillations to be generated so as to form upon current flow across the electrodes an oscillatory circuit resonant at the frequency of said oscillations, and said pole member and the outer surface of the plate from which it extends being dimensioned to form a second oscillatory circuit resonant at substantially the same frequency as said first oscillatory circuit, and means for energizing said nrst oscillatory circuit.

14. A short wave oscillatory spark circuit comprising a plate member having a normally extending flange at the periphery from one surface thereof, a second plate member and an insulating annular element supporting said plate member to said flange whereby said plate members are disposed with opposed surfaces in closed parallel relationship to each other, a pair of electrodes mounted on said opposed surfaces and extending towards each other and means mounting said first plate element having means positioned opposite the location of said electrodes at the back of said first plate for adjustably moving said plate at its center whereby the distance of said electrodes may be adjusted one to the other.

15. In an ultra high frequency spark oscillator, the combination of a metallic plate and a sparking electrode of high melting-point metal different from that of the plate mounted thereon, said electrode and the surface of the plate being part of an ultra high frequency circuit, and the surface of the joint between Said electrode and said plate being smooth and continuous.

HUGO BENIOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,232,559 Rice Feb. 18, 1941 2,002,181 Ilberg May 21, 1935 1,626,030 Eastman Apr. 26, 1927 1,634,627 Osborn July 5, 1927 2,225,105 Flynt Dec. 17, 1940 2,032,926 Ford Mar. 3, 1936 

